1. Fuel on protein

Start reading food labels to get a sense of how many calories you're already eating. Then, add 500 to that number and start eating that many calories every day. Aim to take in about 1g of protein per pound of bodyweight each day, 'cus you're probably not eating enough protein.

2. Limit cardio

Ever thought about how much cardio can you do without losing muscle? Stick by this: You can do up to two days of light jogging on the treadmill, but keep it to around 30 minutes per session. To lose fat while sparing muscle, you'd do even better to perform sprint intervals; for instance, running all-out for a minute, then backing off to a light jog for two minutes. Do this for 30 minutes, three times a week.

3. Lower your reps

Yes, there really is a rep range that builds the most muscle. Do no more than 20 sets per muscle group; closer to 12 is even better. Your reps should be between 6-12 per set for the most muscle growth, and your workouts should never last much longer than 45 minutes. In lieu of more volume, use heavier weights and move through each rep at a controlled speed. Your sets should last between 40-70 seconds; any less, and you're not tensing your muscles long enough to shock them into growth.

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4. Focus on total-body or split routines

Not sure if it's better to do three full-body routines or body-part specific workouts each week? You'll get the best results from your workout by either training the entire body in a single workout or concentrating only on the upper body in one session and the lower body in another. There are advantages to each setup, but both are better than trying to isolate one muscle group in a single session. Concentrate on lifts that involve lots of muscles at once, such as squats, deadlifts, presses, rows, and pullups.

5. Stretch it out

Stretching of any kind (static, getting into a stretched position and holding it—or dynamic, moving fluidly in and out of position), using a foam roller, and getting massages will all help keep you flexible, prevent injury, and improve recovery between workouts.

6. Eat regularly

You should wolf down five to six small meals a day, especially if you're a hardgainer. As long as good-quality fuel keeps coming into your body—particularly protein and carbs—you'll have the calories to build muscle and the metabolism boost to lose fat.

7. Change up your routine

Every four to six weeks you need to alter some part of your routine—whether it's the number of reps you do, the amount of time you rest, the exercises you perform, or any other training variable. Keep a journal of your workouts to record your progress.

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8. Incorporate full-body exercises

The more muscles you involve, either in one exercise or one training session, the greater the hormone release you'll get from your training—that stimulates muscle growth all day long. Hitting each muscle group with roughly the same volume (such as five sets of rows after five sets of bench presses) will ensure balanced training, allowing you to grow quickly and safely, avoiding injuries and preserving flexibility.

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9. Drink shakes

Surround your workout with nutrition, starting with a high-protein and -carbohydrate meal about an hour beforehand. Mix up a protein shake that has a ratio of about 2g of carbs for every 1g of protein, and sip that throughout your workout. Afterward, finish the drink or mix a new one and drink that quickly. Believe it or not, whole foods are not the best option post-workout as they take too long to digest.

10. Rest & recover

The ideal amount of sleep is seven to eight hours per night. You can let loose a night or two each week. But when you do, try to make up for it ASAP. Train no more than four times a week. As for your job, do whatever you can to avoid excess stress; chronic nervousness elevates cortisol, a hormone that makes your body store fat and burn muscle.